Sidechain Launch Kit

Introduction

This directory contains python scripts to tests and explore side chains.

This document walks through the steps to setup a side chain running on your local machine and make your first cross chain transfers.

Get Ready

This section describes how to install the python dependencies, create the environment variables, and create the configuration files that scripts need to run correctly.

Build rippled

Checkout the sidechain branch from the rippled repository, and follow the usual process to build rippled.

Set up Python environment

To make it easy to manage your Python environment with xrpl-py, including switching between versions, install pyenv and follow these steps:

• Install pyenv:

    brew install pyenv
  

  For other installation options, see the pyenv README.

• Use pyenv to install the optimized version for xrpl-py (currently 3.9.1):

    pyenv install 3.9.1
  

• Set the global version of Python with pyenv:

    pyenv global 3.9.1
  

Set up shell environment

To enable autocompletion and other functionality from your shell, add pyenv to your environment.

These steps assume that you're using a Zsh shell. For other shells, see the pyenv README.

• Add pyenv init to your Zsh shell:

  > ~/.zshrc ">

    echo -e 'if command -v pyenv 1>/dev/null 2>&1; then\n  eval "$(pyenv init -)"\nfi' >> ~/.zshrc
  

• Source or restart your terminal:

    . ~/.zshrc
  

Manage dependencies and virtual environments

To simplify managing library dependencies and the virtual environment, xrpl-py uses poetry.

• Install poetry:

    curl -sSL https://raw.githubusercontent.com/python-poetry/poetry/master/get-poetry.py | python -
    poetry install
  

Environment variables

The python scripts need to know the locations of two files and one directory. These can be specified either through command line arguments or by setting environment variables.

1. The location of the rippled executable used for main chain servers. Either set the environment variable RIPPLED_MAINCHAIN_EXE or use the command line switch --exe_mainchain. Until a new RPC is integrated into the main branch (this will happen very soon), use the code built from the sidechain branch as the main chain exe.
2. The location of the rippled executable used for side chain servers. Either set the environment variable RIPPLED_SIDECHAIN_EXE or use the command line switch --exe_sidechain. This should be the rippled executable built from the sidechain branch.
3. The location of the directory that has the rippled configuration files. Either set the environment variable RIPPLED_SIDECHAIN_CFG_DIR or use the command line switch --cfgs_dir. The configuration files do not exist yet. There is a script to create these for you. For now, just choose a location where the files should live and make sure that directory exists.

Setting environment variables can be very convient. For example, a small script can be sourced to set these environment variables when working with side chains.

Creating configuration files

Assuming rippled is built, the three environment variables are set, and the python environment is activated, run the following script:

bin/sidechain/python/create_config_files.py --usd

There should now be many configuration files in the directory specified by the RIPPLED_SIDECHAIN_CFG_DIR environment variable. The --usd creates a sample cross chain assert for USD -> USD transfers.

Running the interactive shell

There is an interactive shell called RiplRepl that can be used to explore side chains. It will use the configuration files built above to spin up test rippled main chain running in standalone mode as well as 5 side chain federators running in regular consensus mode.

To start the shell, run the following script:

bin/sidechain/python/riplrepl.py

The shell will not start until the servers have synced. It may take a minute or two until they do sync. The script should give feedback while it is syncing.

Once the shell has started, the following message should appear:

Welcome to the sidechain test shell.   Type help or ? to list commands.

RiplRepl> 

Type the command server_info to make sure the servers are running. An example output would be:

RiplRepl> server_info
           pid                                  config  running server_state  ledger_seq complete_ledgers
main 0  136206  main.no_shards.mainchain_0/rippled.cfg     True    proposing          75             2-75
side 0  136230                 sidechain_0/rippled.cfg     True    proposing          92             1-92
     1  136231                 sidechain_1/rippled.cfg     True    proposing          92             1-92
     2  136232                 sidechain_2/rippled.cfg     True    proposing          92             1-92
     3  136233                 sidechain_3/rippled.cfg     True    proposing          92             1-92
     4  136234                 sidechain_4/rippled.cfg     True    proposing          92             1-92

Of course, you'll see slightly different output on your machine. The important thing to notice is there are two categories, one called main for the main chain and one called side for the side chain. There should be a single server for the main chain and five servers for the side chain.

Next, type the balance command, to see the balances of the accounts in the address book:

RiplRepl> balance
                           balance currency peer limit
     account                                          
main root    99,999,989,999.999985      XRP           
     door             9,999.999940      XRP           
side door    99,999,999,999.999954      XRP           

There are two accounts on the main chain: root and door; and one account on the side chain: door. These are not user accounts. Let's add two user accounts, one on the main chain called alice and one on the side chain called bob. The new_account command does this for us.

RiplRepl> new_account mainchain alice
RiplRepl> new_account sidechain bob

This just added the accounts to the address book, but they don't exist on the ledger yet. To do that, we need to fund the accounts with a payment. For now, let's just fund the alice account and check the balances. The pay command makes a payment on one of the chains:

RiplRepl> pay mainchain root alice 5000
RiplRepl> balance
                           balance currency peer limit
     account                                          
main root    99,999,984,999.999969      XRP           
     door             9,999.999940      XRP           
     alice            5,000.000000      XRP           
side door    99,999,999,999.999954      XRP           
     bob                  0.000000      XRP      

Finally, let's do something specific to side chains: make a cross chain payment. The xchain command makes a payment between chains:

RiplRepl> xchain mainchain alice bob 4000
RiplRepl> balance
                           balance currency peer limit
     account                                          
main root    99,999,984,999.999969      XRP           
     door            13,999.999940      XRP           
     alice              999.999990      XRP           
side door    99,999,995,999.999863      XRP           
     bob              4,000.000000      XRP           

Note: the account reserve on the side chain is 100 XRP. The cross chain amount must be greater than 100 XRP or the payment will fail.

Making a cross chain transaction from the side chain to the main chain is similar:

RiplRepl> xchain sidechain bob alice 2000
RiplRepl> balance
                           balance currency peer limit
     account                                          
main root    99,999,984,999.999969      XRP           
     door            11,999.999840      XRP           
     alice            2,999.999990      XRP           
side door    99,999,997,999.999863      XRP           
     bob              1,999.999990      XRP    

If you typed balance very quickly, you may catch a cross chain payment in progress and the XRP may be deducted from bob's account before it is added to alice's. If this happens just wait a couple seconds and retry the command. Also note that accounts pay a ten drop fee when submitting transactions.

Finally, exit the program with the quit command:

RiplRepl> quit
Thank you for using RiplRepl. Goodbye.


WARNING: Server 0 is being stopped. RPC commands cannot be sent until this is restarted.

Ignore the warning about the server being stopped.

Conclusion

Those two cross chain payments are a "hello world" for side chains. It makes sure you're environment is set up correctly.